Our goal is to understand the process and mechanisms of the evolution of duplicate genes in eukaryotic genomes. Several eukaryotic genomes have been completed and several more are soon to be completed. The huge amounts of genomic sequence data are very useful for studying various aspects of the evolution of duplicate genes. This is the first time that evolution of duplicate genes can be studied at the genomic level. To seize this unprecedented opportunity, we propose to pursue the following studies: 1. To develop methods for detecting duplicate genes in a genome and for classifying proteins into families. 2. To develop methods for detecting block duplications in a genome. A computer software package for the methods in (1) and (2) will be developed. 3. To assess the extents of gene duplication in various eukaryotic genomes. For each complete genome we ask: How many duplicate genes (gene families) exist in the genome? How often block duplication occurs? Then in comparison among genomes, we shall ask, "which genes have not been duplicated in any of the genomes studied, which duplicate genes are common to diverse genomes and which are restricted to only certain evolutionary lineages? And why are they so distributed?" 4. To study the rate of gene duplication in a genome. 5. To study the mechanisms of evolution of duplicate genes or how duplicate genes evolve following the duplication event. We shall examine various models for the retention and evolution of duplicate genes.